You'll be alright as long as the pipe doesn't wrinkle like the shitty pipe sections they use at muffler shops. Mandrel is the best of course, but a tubing bender can do an ok job as long as you're not doing tight bends.

Other option is to buy sections of mandrel bent online, and cut/weld in sections of bend as you need them

Check out these guys. Some of teh better prices I've found.
http://store.racing-solutions.org/info.html

 

BTW, you're crazy for taking the car w/o a title. What paperwork did you have that proved you actually paid for it, in case the guy decided to keep your money, and tell the cops you stole his car?

That was my worst fear when I bought my current TT. Guy had a lien on it, said he'd mail me the title after he paid off the car (with my money) to free the title.

Hmm, pay off your car, while you legally own it, with my money? Don't think so....

 

I would drive to a shop that can mandrel bend pipe !!! less restrictions=more flow=more power !!!